Antinuclear antibodies (ANAs) have been identified in patients with interstitial cystitis (IC). As determined by unique immunofluorescence staining patterns and by specificities on Western blots, most are ANAs which recognize novel autoantigens compared to those from patients with systemic autoimmune diseases such as lupus or scleroderma. In an antigen- driven mechanism for the autoimmune response in IC, we hypothesize that the molecular identity of autoantibodies and their target antigens may provide insights into the diagnosis and/or pathogenesis of IC by reflecting pathways activated as a result of chronic bladder inflammation and injury. To test our overall hypothesis, the objectives of this proposal are to definitively characterize the profiles and fine specificities of autoantibodies in the sera of patients with interstitial cystitis. This characterization will be accomplished by immunofluorescence microscopy, Western blotting, and immunoprecipitation of radioactively labeled proteins and RNAs. It has already been shown that some antigens reacting with antibodies from IC patients remain unidentified. A number of sera which recognize unknown antigens will be selected as cloning reagents to probe cDNA expression libraries. Analyses of the nucleic acid and protein sequences of the cloned antigens will be used to determine if characteristic structural and functional motifs are present in these antigens, information that might aid in their identification. Recombinant protein antigens will be generated from the cDNA clones and the authenticity of the recombinant proteins verified in an ELISA with the original sera used for library screening. It will then be possible, by means of ELISA, to ascertain whether autoantibodies to these antigens are unique for IC or are also present at low incidence in systemic autoimmune diseases. ff unique to IC, their detection could prove useful in diagnosis and classification of the IC patient population.